Optical path switching device

ABSTRACT

With the invention, it is possible to suppress losses of light for monitoring and enhances the optical confinement efficiency into an optical fiber for output over the related art. The optical path switching device  20  includes: a platform  22  housed in an enclosure  21  and mounting various types of optical components; optical fiber collimators  23, 24  as optical input means; an optical fiber collimator  25  as optical output means; a parallelogram prism  26  for switching over the optical path between the optical fiber collimators  23, 24  and  25  based on a change in its position; and light receiving elements  31, 32  for detecting a portion of the light inputted from the optical fiber collimators  23, 24  in order to monitor the light; and controls the position of the parallelogram prism  26  in accordance with the monitoring result of the light. The light receiving elements  31, 32  are arranged to detect only a portion of the light in the outer part in radial direction.

TECHNICAL FIELD

The present invention relates to an optical path switching device whichis used, for example, as an optical device in an optical communicationsystem and which switches over the optical path.

BACKGROUND ART

In the related art, an optical path switching device is known forswitching over the optical path of a prism for optical switches bymechanically causing the prism to enter or exit from an optical path(move the prism between a position off the optical path and a positionon the optical path), the optical path switching device designed tobranch a portion of light at a predetermined ratio by way of an opticalbranching device and detect the branched light byway of a lightreceiving element (for example, refer to Patent Reference 1). The lightquantity level of the light detected by the light receiving element ismonitored by a light receiving circuit. The monitoring result may beused for the mechanical movement (entry/exit to/from an optical path) ofthe prism for optical switches. For example, in case the level of thereceived light detected by the light receiving element is below apredetermined level, a separately arranged controller drives means formoving a prism for optical switches. By moving the prism for opticalswitches from a position off the optical path to a position on theoptical path, it is possible to switch over the optical path.

Patent Reference 1: JP-A-2003-21756 (FIG. 1, Page 5)

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

The related art optical path switching device uses a half mirror as anoptical branching device for obtaining light for monitoring. The halfmirror separates invading light into transmitted light and reflectedlight and guides the latter (reflected light) to a light receivingelement and the former (transmitted light) to an optical fibercollimator for output. The light invading the optical fiber collimatorfor output is confined in an optical fiber while centered about theaxial center of the luminous flux (portion with high quantity ofconcentrated light as viewed along the section of the light) by usingcondensing feature of the collimator lens. Note that the condensingperformance of the collimator lens has certain limits. The half mirroras an optical branching device in a related art optical path switchingdevice operates on all regions of the luminous flux to branches light.The half mirror also branches a portion of light near the axial centerof the luminous flux, which invites losses of light. Thus, the relatedart optical path switching device does not have excellent opticalconfinement efficiency into an optical fiber for output.

The invention has been accomplished to solve the related art problems.An object of the invention is to provide an optical path switchingdevice capable of enhancing optical confinement efficiency into anoptical fiber for output over the related art.

Means for Solving the Problems

The inventive optical path switching device comprises: at least oneoptical input means including an optical fiber and a lens for inputtingan optical signal; at least one optical output means including anoptical fiber and a lens for outputting an optical signal; an opticalpath switching component for switching over the optical path between theoptical input means and the optical output means based on a change inits state; and an optical detection component for detecting a portion ofthe light inputted from the optical inputting means in order to monitorthe light; the optical detection component controlled in accordance withthe monitoring result of the light, characterized in that the opticaldetection component detects only a portion of the light in the outerpart in radial direction.

With this configuration, an optical component detects only a portion oflight inputted as an optical signal in the outer part in radialdirection (that is, the light except near the axial center effective forconfinement into the optical fiber). The optical path switching deviceof the invention suppresses losses of light for monitoring over therelated art and enhances the optical confinement efficiency into anoptical fiber for output over the related art.

The optical path switching device of the invention comprises opticalbranching means for branching only a portion of the light inputted fromthe optical input means in the outer part in radial direction and theoptical detection component detects the light branched by this opticalbranching means.

With this configuration, the optical path switching device of theinvention may reduce the restrictions on the mounting position of anoptical detection component by appropriately setting the position anddirection of the optical branching means, thus enhancing the freedom ofdesign.

In the optical path switching device of the invention, the opticaldetection component is arranged in a position on which is directlyincident only a portion of light inputted from the optical input meansin the outer part in radial direction.

This configuration eliminates the optical branching means from theoptical path switching device of the invention thus reducing the numberof components.

Advantage of the Invention

The invention provides an optical path switching device capable ofenhancing optical confinement efficiency into an optical fiber foroutput over the related art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an optical communication system accordingto a first embodiment of the invention.

FIG. 2 shows the side surface section of the optical communicationsystem shown in FIG. 1.

FIG. 3A shows the top surface section of the optical path switchingdevice shown in FIG. 2.

FIG. 3B shows the top surface section of the optical path switchingdevice shown in FIG. 2 in a state different from that shown in FIG. 3A.

FIG. 4 is a top view of the reflecting mirror of the optical pathswitching device shown in FIG. 2.

FIG. 5 shows the side surface section of the optical communicationsystem according to the first embodiment of the invention in aconfiguration different from that shown in FIG. 2.

FIG. 6A shows the top surface section of the optical path switchingdevice of the optical communication system according to the secondembodiment of the invention.

FIG. 6B shows the top surface section of the optical path switchingdevice shown in FIG. 6A in a state different from that shown in FIG. 6A.

FIG. 7 is a top view of the glass block of the optical path switchingdevice shown in FIGS. 6A and 6B.

FIG. 8 is a top view of the glass block of the optical path switchingdevice of the optical communication system according to the secondembodiment of the invention in a configuration different from that shownin FIG. 7.

FIG. 9A shows the top surface section of the optical path switchingdevice of the optical communication system according to the thirdembodiment of the invention.

FIG. 9B shows the top surface section of the optical path switchingdevice shown in FIG. 9A in a state different from that shown in FIG. 9A.

FIG. 10 is a top view of the reflecting mirror of the optical pathswitching device shown in FIG. 9.

FIG. 11A shows the top surface section of the optical path switchingdevice of the optical communication system according to the fourthembodiment of the invention.

FIG. 11B shows the top surface section of the optical path switchingdevice shown in FIG. 11A in a state different from that shown in FIG.11A.

FIG. 12 is a top view of the reflecting mirror of the optical pathswitching device shown in FIGS. 11A and 11B.

FIG. 13 is a top view of a lens including a reflecting film formedthereon in place of the reflecting mirror shown in FIG. 12.

FIG. 14A shows the top surface section of the optical path switchingdevice of the optical communication system according to the fifthembodiment of the invention.

FIG. 14B shows the top surface section of the optical path switchingdevice shown in FIG. 14A in a state different from that shown in FIG.14A.

FIG. 15A shows the top surface section of the optical path switchingdevice of the optical communication system according to the sixthembodiment of the invention.

FIG. 15B shows the top surface section of the optical path switchingdevice shown in FIG. 15A in a state different from that shown in FIG.15A.

FIG. 16 is a top view of the prism of the optical path switching deviceshown in FIG. 15.

FIG. 17A shows the top surface section of the optical path switchingdevice of the optical communication system according to the seventhembodiment of the invention.

FIG. 17B shows the top surface section of the optical path switchingdevice shown in FIG. 17A in a state different from that shown in FIG.17A.

FIG. 18 is a top view of the light receiving element of the optical pathswitching device shown in FIGS. 17A and 17B.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

20: Optical path switching device

26: Parallelogram prism (optical path switching component)

31, 32: Light receiving element (light detecting component)

40: Optical path switching device

60: Optical path switching device

80: Optical path switching device

180: Optical path switching device

200: Optical path switching device

220: Optical path switching device

240: Optical path switching device

280: Optical path switching device

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be described referring to figures.

First Embodiment

The configuration of an optical communication system according to thefirst embodiment will be described.

As shown in FIG. 1, an optical communication system 10 comprises: anoptical transmitter 11 for transmitting an optical signal; an opticalreceiver 12 for receiving an optical signal; an optical branching device13 for branching the optical signal transmitted by the opticaltransmitter 11 to two lines; a mechanism optical path switching device20 for inputting an optical signal from each of the lines branched bythe optical branching device 13 and outputting an optical signalreceived by the optical receiver 12; and a controller 14 for controllingthe operation of the optical path switching device 20 so as to cause theoptical receiver 12 to receive any one of the optical signals inputtedfrom the two lines branched by the optical branching device 13.

As shown in FIG. 2, the optical path switching device 20 is installed onthe printed-circuit board 15 on which the controller 14 (refer toFIG. 1) is also installed. The optical path switching device 20 and thecontroller 14 are electrically connected to each other via aprinted-circuit board 15.

As shown in FIGS. 2 3A and 3B, the optical path switching device 20includes an enclosure 21 and a platform 22 housed in the enclosure 21and mounting various types of optical components. The platform 22mounts: an input optical fiber collimator 23 as optical input means forinputting an optical signal from one of the two lines branched by theoptical branching device 13 (refer to FIG. 1); an input optical fibercollimator 24 as another optical input means for inputting an opticalsignal from the other of the two lines branched by the optical branchingdevice 13; and an output optical fiber collimator 25 as optical outputmeans for outputting an optical signal received by the optical receiver12 (refer to FIG. 1). The optical path switching device 20 furtherincludes a parallelogram prism as an optical path switching componentfor switching over the optical path based on a change in its position,that is, a change in its state in a direction orthogonal to the platform22 shown by an arrow 22 a (direction from the platform 22 to theprinted-circuit board 15; hereinafter referred to as the downwarddirection) and a direction shown by an arrow 22 b (direction from theplatform 22 to the top surface of the enclosure 21; hereinafter referredto as the downward direction) opposite to the direction shown by thearrow 22 a; an actuator 27 for moving the parallelogram prism 26 invertical direction shown by the arrow 22 a and the arrow 22 b; arectangular prism 28 for changing the direction of travel of light;reflecting mirrors 29, 30 for totally reflecting incident light; lightreceiving elements 31, 32 as an optical component for detecting light;and a light-absorbing bodies 33, 34 for absorbing light.

To the platform 22 are fixed optical fiber collimators 23 through 25, arectangular prism 28, reflecting mirrors 29, 30, light receivingelements 31, 32, and the light-absorbing body 34. The light-absorbingbody 33 is fixed to the parallelogram prism 26.

The optical fiber collimator 23 is composed of an optical fibercollimator 23 a and a lens 23 b. Similarly, the optical fiber collimator24 is composed of an optical fiber collimator 24 a and a lens 24 b.Similarly, the optical fiber collimator 25 is composed of an opticalfiber collimator 25 a and a lens 25 b.

The parallelogram prism 26 includes reflecting mirrors 26 a, 26 b in theform of a film mounted thereon for totally reflecting incident light. Incase the reflecting surface is used under the total reflectioncondition, a reflecting film may be removed. Providing ananti-reflection film on the light incident surface enhances thetransmission efficiency.

The rectangular prism 28 includes reflecting mirrors 28 a, 28 b in theform of a film mounted thereon for totally reflecting incident light. Incase the reflecting surface is used under the total reflectioncondition, a reflecting film may be removed. Providing ananti-reflection film on the light incident surface enhances thetransmission efficiency.

The light receiving elements 31, 32 are arranged in positions on theoptical path to detect light upstream of the parallelogram prism 26 onthe optical path.

The light receiving elements 31, 32 are designed to convert a detectedoptical signal to an electric signal and output the same to thecontroller 14 (refer to FIG. 1). The actuator 27 is designed to move theparallelogram prism 26 in accordance with a control signal received fromthe controller 14.

As shown in FIG. 4, the reflecting mirror 29 is arranged in a positionon which is incident only a portion (hereinafter described as 5% as anexample) of light 23A outputted from the optical fiber collimator 23 inthe outer part in radial direction. The reflecting mirror 29 thusreflects and branches 5% of the light 23A outputted from the opticalfiber collimator 23. Similarly, the reflecting mirror 30 is arranged ata position on which is incident only a portion (5%) of light outputtedfrom the optical fiber collimator 24 in the outer part in radialdirection. The reflecting mirror 30 thus reflects and branches 5% of thelight outputted from the optical fiber collimator 24. The lightbranching ratio may be arbitrarily set depending on the position of areflecting mirror in the radial direction of light. A branching ratiothat may be set arbitrarily is generally specified within a practicalrange of 0.1 to 20%.

The operation of the optical communication system 10 will be described.

An optical signal transmitted by the transmitter 11 is branched to twolines by the optical branching device 13 and respective optical signalsare inputted to the optical path switching device 20.

The optical path switching device 20 converts the quantity of light intorespective electric signals and outputs the electric signals to thecontroller 14. The controller 14 determines whether any one of the twolines branched by the optical branching device 13 is faulty based on anelectric signal inputted from the optical path switching device 20 andcontrol the operation of the optical path switching device 20 so as tocause the optical receiver 12 to receive an optical signal inputted froman unaffected line.

The term “faulty” refers to a case where the actual light quantity levelor wavelength is out of a predetermined value range. A light quantitylevel exceeding or below a predetermined light quantity level or awavelength shorter than or longer than a predetermined wavelengthcorresponds to a fault. In order to check for such a fault, the opticalpath switching device 20 branches a portion of light with the reflectingmirrors 29, 30 and detects the branched light by way of the lightreceiving elements 31, 32 to perform monitoring of an optical signal.

The optical receiver 12 receives an optical signal passing through anunaffected line out of the lines between the optical branching device 13and the optical path switching device 20.

The operation of the optical path switching device 20 will be describedin detail. The controller 14 calculates the quantity of light emittedfrom the optical fiber collimator 23 based on an electric signal comingfrom the light receiving element 31. Assuming the ratio of quantity oflight reflected by the reflecting mirror 29 to the quantity of light 23Aoutputted from the optical fiber collimator 23 (5% in the aboveexample), the quantity of light received by the light receiving element31, and the quantity of light emitted from the optical fiber collimator23 respectively as R, p1 and P, P may be calculated using Expression 1.

P=p1/R  [Expression 1]

When the quantity of light emitted from the optical fiber collimator 23is within a predetermined range, the controller 14 determines that aline connected to the optical fiber collimator 23 is not faulty andtransmits a control signal to the actuator 27 so as to place theparallelogram prism 26 on standby at the lower end of the travel rangein the downward direction shown by the arrow 22 a (position theparallelogram prism 26 has deviated from the optical path: position offthe optical path). The actuator 27 thus places the parallelogram prism26 on standby in a position off the optical path in accordance with acontrol signal coming from the controller 14.

When the parallelogram prism 26 is in a position off the optical path,the light inside the optical path switching device 20 travels as shownby arrows in dotted lines in FIG. 3A. That is, of the light outputtedfrom the optical fiber collimator 23, 5% is reflected by the reflectingmirror 29 and detected by the light receiving element 31 while 95%travels in the upward direction shown by the arrow 22 b with respect tothe parallelogram prism 26, is re-directed by the reflecting mirrors 28a, 28 b of the rectangular prism 28, and is inputted to the opticalfiber collimator 25. Of the light outputted from the optical fibercollimator 24, 5% is reflected by the reflecting mirror 30 and detectedby the light receiving element 32 while 95% travels in the upwarddirection shown by the arrow 22 b with respect to the parallelogramprism 26 and is absorbed by the light-absorbing body 34.

Thus, when the controller 14 has determined that a line connected to theoptical fiber collimator 23 is not faulty, an optical signal that haspassed through the line connected to the optical fiber collimator 23 isreceived by the optical receiver 12.

The wavelength of the light reflected on the mirror 29 may be the wholespectrum of the wavelength of the incident light or a portion thereof.

When the quantity of light emitted from the optical fiber collimator 23is out of a predetermined range, the controller 14 determines that aline connected to the optical fiber collimator 23 is faulty andtransmits a control signal to the actuator 27 so as to move theparallelogram prism 26 to the upper end of the travel range in theupward direction shown by the arrow 22 b (position the parallelogramprism 26 intercepts the optical path: position on the optical path). Theactuator 27 thus moves the parallelogram prism 26 to a position on theoptical path in accordance with a control signal coming from thecontroller 14.

When the parallelogram prism 26 is in a position on the optical path,the light inside the optical path switching device 20 travels as shownby arrows in dotted lines in FIG. 3B. That is, of the light outputtedfrom the optical fiber collimator 23, 5% is reflected by the reflectingmirror 29 and detected by the light receiving element 31 while 95% isabsorbed by the light-absorbing body 33 fixed to the parallelogram prism26. Of the light outputted from the optical fiber collimator 24, 5% isreflected by the reflecting mirror 30 and detected by the lightreceiving element 32 while 95% is re-directed by the reflecting mirrors26 a, 26 b of the parallelogram prism 26 as well as the reflectingmirrors 28 a, 28 b of the rectangular prism 28, and is inputted to theoptical fiber collimator 25.

Thus, when the controller 14 has determined that a line connected to theoptical fiber collimator 23 is faulty, an optical signal that has passedthrough the line connected to the optical fiber collimator 24 isreceived by the optical receiver 12.

The controller 14 constantly monitors whether a line connected to theoptical fiber collimator 24 is faulty based on an electric signal comingfrom the light receiving element 32.

Monitoring of the optical signal may be made on the quantity of lightincident on a light receiving element as well As the wavelength,frequency, phase of light included in an optical signal or an encodedsignal. That is, the controller 14 may transmit a control signal to theactuator 27 to switch over the optical path when detecting thepredetermined wavelength of light or waveform itself (such as frequency,phase or encoded signal). For example, in a certain transmission system,when the transmission speed of an optical signal traveling from theoptical transmitter 11 to the optical receiver 12 exceeds 10 Gbps, thewavelength of light, frequency or phase of the optical signal changesthus causing a line fault. In such a transmission system, all phenomenaof malfunction may be determined as a line fault and an alternateoptical path may be selected.

As described above, the optical path switching device 20 is designed tobranch only a portion of light outputted from the optical fibers 23, 24in the outer part in radial direction byway of the reflecting mirrors29, 30 and detect the branched light with the light receiving elements31, 32. This suppresses losses of light for monitoring and enhances theoptical confinement efficiency into an optical fiber for output. Theoptical path switching device 20 arranges the light receiving elements31, 32 in positions on the optical path to detect light upstream of theparallelogram prism 26 as an optical path switching component.

With the optical path switching device 20, the reflecting mirrors 29, 30totally reflect incident light thus reducing the Polarization DependentLoss (PDL). Moreover, general mirrors may be used as the reflectingmirrors 29, 30.

As shown in FIG. 5, the optical path switching device 20 may arrange thelight receiving elements 31, 32 in the direction shown by the arrow 22 awith respect to each of the reflecting mirrors 29, 30 and fix thereflecting mirrors 29, 30 diagonally with respect to the platform 22 soas to reflect a portion of light outputted from the optical fibercollimators 23, 24 in the direction shown by the arrow 22 a toward eachof the light receiving elements 31, 32. The configuration of the opticalpath switching device 20 shown in FIG. 5 may be of a more compact designthan that shown in FIG. 3. In the configuration of the optical pathswitching device 20 shown in FIG. 5, the length of wiring from the lightreceiving elements 31, 32 to the printed-circuit board 15 is longer thanthat shown in FIG. 3. Thus, the configuration of the optical pathswitching device 20 shown in FIG. 5 is less vulnerable to disturbancenoise even when only a faint signal is outputted from the lightreceiving elements 31, 32 than that shown in FIG. 3.

The optical path switching device 20 includes a member serving as thereference surface of each of the optical components such as the opticalfiber collimators 23 through 25 and the parallelogram prism 26, that is,the platform 22 functioning as an optical flat. This provides thepositioning accuracy of each optical component on the submicron orderand maintains the position of each optical component despite a change inthe ambient temperature of humidity.

Second Embodiment

The configuration of an optical communication system according to thesecond embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system 10 according to the first embodiment (refer toFIG. 1) will be given the same sign as that of the configuration of theoptical communication system 10 and the corresponding details will beomitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication system 10except that a mechanical optical path switching device 80 shown in FIGS.6A and 6B is used instead of the optical path switching device 20 (referto FIG. 3).

The configuration of the optical path switching device 80 is similar tothat of the optical path switching device 20 except that glass blocks81, 82 including reflecting mirrors 81 a, 82 a for totally reflectingincident light are respectively formed of films is used instead of thereflective mirrors 29, 30 (refer to FIG. 3) and that the light receivingelements 31, 32 are fixed to different positions on the platform 22 fromthose in the optical path switching device 20.

The glass blocks 81, 82 are fixed to the platform 22.

As shown in FIG. 7, the glass block 81 is arranged in a position onwhich is incident only a portion of light 23A outputted from the opticalfiber collimator 23 on the outer periphery in radial direction so as toreflect a portion of light 23A outputted from the optical fibercollimator 23. The glass block 81 is arranged so that an angle 81Cformed by the light incident surface 81A and the light reflectingsurface 81B of the light 23A outputted from the optical fiber collimator23 will be 45 degrees, for example, and that the light incident surface81A will be nearly perpendicular to the travel direction of the light23A. While description has been made on the glass block 81, the same istrue to the glass block 82.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication system10 according to the first embodiment (refer to FIG. 1) so that thecorresponding details will be omitted.

When a controller 14 has determined that a line connected to the opticalfiber collimator 23 is not faulty, light inside the optical pathswitching device 80 travels as shown by arrows in dotted lines in FIG.6A. When the controller 14 has determined that a line connected to theoptical fiber collimator 23 is faulty, the light inside the optical pathswitching device 80 travels as shown by arrows in dotted lines in FIG.6B.

As described above, the optical path switching device 80 branches only aportion of light outputted from the optical fibers 23, 24 by way of theglass blocks 81, 82 in the outer part in radial direction and detectsthe branched light with the light receiving elements 31, 32. Thissuppresses losses of light for monitoring and enhances the opticalconfinement efficiency into an optical fiber for output.

In the optical path switching device 80, the glass block 81 is arrangedso that the light incident surface 81A of the glass block 81 will bealmost perpendicular to the travel direction of the light 23A outputtedfrom the optical fiber collimator 23. It is thus possible to apply alow-cost antireflection film on the light incident surface 81A of theglass block 81. In the optical path switching device 80, the reflectingmirror 81 a of the glass block 81 totally reflect incident light so thatit is possible to form the reflecting mirror 81 a with a generallow-cost reflecting film. In case the refractivity of the glass block 81is 1.5 and the light incident surface of light determined by the angleformed by the optical axis of the light and the light reflecting surface81 a exceeds 41.9 degrees, the total reflection condition is satisfiedand a reflectivity of 100% is attained without using a reflecting film.The optical path switching device 80 includes the glass block 81 with alarge installation area on the platform 22 instead of the thinreflecting mirror 29 (refer to FIGS. 3A and 3B) as in the optical pathswitching device 20 according to the first embodiment (refer to FIGS. 3Aand 3B). This facilitates the work of fixing the reflecting mirror 81 ato the platform 22 and reduces the workload of minute adjustment of theinclination of the reflecting mirror 81 a with respect to the platform22. The optical path switching device 80 includes the glass block 81with a large installation area on the platform 22 instead of the thinreflecting mirror 29 as in the optical path switching device 20. Thisprevents possible inclination of the reflecting mirror 81 a over timewith respect to the platform 22 due to poor quality or degradedcharacteristic of an adhesive used for fixing thus maintaining thereliability of detection of an optical signal for a long period. Whiledescription has been made on the glass block 81, the same is true to theglass block 82.

As shown in FIG. 10, the angle 81C of the glass block 81 may be lessthan 45 degrees. In case the angle 81C of the glass block 81 in theoptical path switching device 80 is less than 45 degrees, the width oflight received by the light receiving element 31 is narrowed to increasethe intensity of light thus enhancing the light-receiving efficiency ofthe light receiving element 31. In case the angle 81C of the glass block81 in the optical path switching device 80 is less than 45 degrees, theluminous flux of light received by the light receiving element 31 isnarrowed thus reducing the light-receiving area of the light receivingelement 31. As a result, a low-cost light receiving element 31 may beused or response of the light receiving element 31 to an optical signalis improved. Moreover, it is possible to reduce noise on an outputsignal from the light receiving element 31. While description has beenmade on the glass block 81, the same is true to the glass block 82.

Third Embodiment

The configuration of an optical communication system according to thethird embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system 10 according to the first embodiment (refer toFIG. 1) will be given the same sign as that of the configuration of theoptical communication system 10 and the corresponding details will beomitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication system 10except that a mechanical optical path switching device 180 shown inFIGS. 9A and 9B is used instead of the optical path switching device 20(refer to FIG. 3).

The configuration of the optical path switching device 180 is similar tothat of the optical path switching device 20 except that reflectingmirrors 181, 182 for totally reflecting incident light are used insteadof the reflective mirrors 29, 30 (refer to FIGS. 3A and 3B) and that thelight receiving elements 31, 32 are fixed to different positions fromthose in the optical path switching device 20.

The reflecting mirror 181 is inserted between an optical fiber 23 a anda lens 23 b and fixed to the platform 22. The reflecting mirror 182 isinserted between an optical fiber 24 a and a lens 24 b and fixed to theplatform 22. The light receiving element 31 is fixed to an enclosure 21in a position in a direction with respect to the light receiving element32 shown by the arrow 22 b (refer to FIG. 2). The light receivingelement 32 is fixed to the platform 22. The reflecting mirror 181 isfixed diagonally to the platform 22 so as to allow reflected light toreach the light receiving element 31 without being obstructed by theoptical fiber collimator 24.

As shown in FIG. 10, the reflecting mirror 182 is arranged in a positionon which is incident only a portion (hereinafter described as 5% as anexample) of light 24A outputted from the optical fiber 24 a in the outerpart in radial direction. The reflecting mirror 182 thus reflects 5% ofthe light 24A outputted from the optical fiber 24 a. While descriptionhas been made on the reflecting mirror 182, the same is true to thereflecting mirror 181.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication system10 according to the first embodiment (refer to FIG. 1) so that thecorresponding details will be omitted.

When a controller 14 has determined that a line connected to an opticalfiber collimator 23 is not faulty, light inside the optical pathswitching device 180 travels as shown by arrows in dotted lines in FIG.9A. When the controller 14 has determined that a line connected to theoptical fiber collimator 23 is faulty, the light inside the optical pathswitching device 180 travels as shown by arrows in dotted lines in FIG.9B.

As described above, the optical path switching device 180 branches onlya portion of light outputted from the optical fibers 23 a, 24 a by wayof the reflecting mirrors 181, 182 in the outer part in radial directionand detects the branched light with the light receiving elements 31, 32.This suppresses losses of light for monitoring and enhances the opticalconfinement efficiency into an optical fiber for output.

The optical path switching device 180 includes the reflecting mirror 181inserted between the optical fiber 23 a and the lens 23 b and thereflecting mirror 182 inserted between the optical fiber 24 a and thelens 24 b, thus providing a more compact design.

Fourth Embodiment

The configuration of an optical communication system according to thefourth embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system 10 according to the first embodiment (refer toFIG. 1) will be given the same sign as that of the configuration of theoptical communication system 10 and the corresponding details will beomitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication system 10except that a mechanical optical path switching device 200 shown inFIGS. 11A and 11B is used instead of the optical path switching device20 (refer to FIGS. 3A and 3B).

The configuration of the optical path switching device 200 is similar tothat of the optical path switching device except that reflecting mirrors201, 202 for totally reflecting incident light are used instead of thereflective mirrors 29, 30 (refer to FIGS. 3A and 3B) and that the lightreceiving elements 31, 32 are fixed to different positions from those inthe optical path switching device 20.

The reflecting mirrors 201, 202 are respectively fixed into lens 23 b,24 b. The light receiving element 31 is fixed to an enclosure 21 in aposition in a direction shown by an arrow 22 b (refer to FIG. 2) withrespect to the light receiving element 32. The light receiving element32 is fixed to the platform 22. The reflecting mirror 201 is fixeddiagonally to the lens 23 b so as to allow reflected light to reach thelight receiving element 31 without being obstructed by the optical fibercollimator 24.

As shown in FIG. 12, the reflecting mirror 202 is arranged in a positionon which is incident only a portion (hereinafter described as 5% as anexample) of light 24A outputted from the optical fiber 24 a in the outerpart in radial direction. The reflecting mirror 202 thus reflects 5% ofthe light 24A outputted from the optical fiber 24 a. While descriptionhas been made on the reflecting mirror 202, the same is true to thereflecting mirror 201. As an alternative to the reflecting mirror 202, adiagonal notch may be made in a lens 24 b′ and a reflecting mirror maybe formed on a slope 202′ formed thereon, as shown in FIG. 13.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication system10 according to the first embodiment (refer to FIG. 1) so that thecorresponding details will be omitted.

When a controller 14 has determined that a line connected to an opticalfiber collimator 23 is not faulty, light inside the optical pathswitching device 200 travels as shown by arrows in dotted lines in FIG.11A. When the controller 14 has determined that a line connected to theoptical fiber collimator 23 is faulty, the light inside the optical pathswitching device 200 travels as shown by arrows in dotted lines in FIG.11B.

As described above, the optical path switching device 200 branches onlya portion of light outputted from the optical fibers 23, 24 by way ofthe reflecting mirrors 201, 202 in the outer part in radial directionand detects the branched light with the light receiving elements 31, 32.This suppresses losses of light for monitoring and enhances the opticalconfinement efficiency into an optical fiber for output.

The optical path switching device 200 includes the reflecting mirrors201, 202 respectively fixed into the lenses 23 b, 24 b, and is thus easyto manufacture.

Fifth Embodiment

The configuration of an optical communication system according to thefifth embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system 10 according to the first embodiment (refer toFIG. 1) will be given the same sign as that of the configuration of theoptical communication system 10 and the corresponding details will beomitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication system 10except that a mechanical optical path switching device 220 shown inFIGS. 14A and 14B is used instead of the optical path switching device20 (refer to FIGS. 3A and 3B).

The configuration of the optical path switching device 220 is similar tothat of the optical path switching device 20 except that a singleoptical fiber collimator 221 to which an optical signal from one of thetwo lines branched by the optical branching device 13 (refer to FIG. 1)and an optical signal from the other of the two lines are inputted isused instead of the optical fiber collimators 23, 24 (refer to FIGS. 3Aand 3B) and that a reflecting mirror 30 and a light receiving element 32are fixed to different positions on the platform 22 from those in theoptical path switching device 20.

The optical fiber collimator 221 is fixed to the platform 22.

The optical fiber collimator 221 is composed of an optical fiber 221 ato which an optical signal from one of the two lines branched by theoptical branching device 13 is inputted, an optical fiber 221 b to whichan optical signal from the other of the two lines branched by theoptical branching device 13 is inputted, and a lens 221 c.

Similar to the first embodiment, reflecting mirrors 29, 30 are arrangedin a position on which is incident only a portion (hereinafter describedas 5% as an example) of light outputted from the optical fibercollimator 221 in width direction. The reflecting mirrors 29, 30 thusreflect 5% of the light outputted from the optical fiber collimator 221.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication system10 according to the first embodiment (refer to FIG. 1) so that thecorresponding details will be omitted.

When a controller 14 has determined that a line connected to the opticalfiber 221 a is not faulty, light inside the optical path switchingdevice 220 travels as shown by arrows in dotted lines in FIG. 14A. Whenthe controller 14 has determined that a line connected to the opticalfiber 221 b is faulty, the light inside the optical path switchingdevice 220 travels as shown by arrows in dotted lines in FIG. 14B.

As described above, the optical path switching device 220 branches onlya portion of light outputted from the optical fibers 23, 24 by way ofthe reflecting mirrors 29, 30 in the outer part in radial direction anddetects the branched light with the light receiving elements 31, 32.This suppresses losses of light for monitoring and enhances the opticalconfinement efficiency into an optical fiber for output.

The optical path switching device 220 includes a single optical fibercollimator 221 instead of two optical fiber collimators 23, 24 (refer toFIGS. 3A and 3B) as in the optical path switching device 20 according tothe first embodiment (refer to FIGS. 3A and 3B). This reduces the numberof processes of fixing optical components on the platform 22.

Similar to the optical path switching device 20 according to the firstembodiment (refer to FIG. 5), the optical path switching device 220 mayarrange the light receiving elements 31, 32 in downward direction shownby an arrow 22 a (refer to FIG. 5) with respect to each of thereflecting mirrors 29, 30. The optical path switching device 220 maydiagonally fix each of the reflecting mirrors 29, 30 to the platform 22so as to reflect a portion of light outputted from the optical fibercollimator 221 in downward direction shown by the arrow 22 a.

Sixth Embodiment

The configuration of an optical communication system according to thesixth embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system according to the fifth embodiment will be given thesame sign as that of the configuration of the optical communicationsystem according to the fifth embodiment and the corresponding detailswill be omitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication systemaccording to the fifth embodiment except that a mechanical optical pathswitching device 240 shown in FIGS. 15A and 15B is used instead of theoptical path switching device 220 (refer to FIGS. 14A and 14B).

The configuration of the optical path switching device 240 is similar tothat of the optical path switching device 220 except that a prism 241including reflecting mirrors 241 a, 241 b for totally reflectingincident light formed by films is used instead of the reflective mirrors29, 30 (refer to FIGS. 14A and 14B).

The prism 241 is fixed to a platform 22. As shown in FIG. 16, the prism241 is arranged in a position on the reflecting mirror thereof isincident only a portion (hereinafter described as 5% as an example) oflight 221A outputted from an optical fiber collimator 221 (refer toFIGS. 15A and 15B) via an optical fiber 221 a (refer to FIGS. 15A and15B) in the outer part in radial direction and on the reflecting mirrorthereof is incident only a portion (hereinafter described as 5% as anexample) of light 221B outputted from the optical fiber collimator 221(refer to FIGS. 15A and 15B) via an optical fiber 221 b (refer to FIGS.15A and 15B) in width direction so as to reflect 5% of each light beam221A, 221B outputted from the optical fiber collimator 221.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication systemaccording to the 11th embodiment so that the corresponding details willbe omitted.

When a controller 14 has determined that a line connected to an opticalfiber 221 a is not faulty, light inside the optical path switchingdevice 240 travels as shown by arrows in dotted lines in FIG. 15A. Whenthe controller 14 has determined that a line connected to the opticalfiber 221 b is faulty, the light inside the optical path switchingdevice 240 travels as shown by arrows in dotted lines in FIG. 15B.

As described above, the optical path switching device 240 branches onlya portion of light outputted from the optical fibers 221 a, 221 b by wayof the reflecting mirrors 241 a, 241 b in the outer part in radialdirection and detects the branched light with the light receivingelements 31, 32. This suppresses losses of light for monitoring andenhances the optical confinement efficiency into an optical fiber foroutput.

In the optical path switching device 240, both the optical fibers 221 a,221 b are coupled to the lens 221 c and the spacing between the opticalfiber 221 a and the optical fiber 221 b is constant. This makes it easyto fix the optical fiber collimator 221 and the prism 241 to theplatform 22 so as to satisfy the alignment therebetween shown in FIG.21.

The prism 241 may be of a size to allow light outputted from the opticalfiber collimator 221 to be totally incident on the reflecting mirrors241 a, 241 b as long as the reflecting mirrors 241 a, 241 b are halfmirrors that reflects a portion (for example 5%) of incident light andtransmits the residual portion of the light.

Seven Embodiment

The configuration of an optical communication system according to theseventh embodiment will be described.

Part of the configuration of the optical communication system accordingto this embodiment similar to the configuration of the opticalcommunication system 10 according to the first embodiment (refer toFIG. 1) will be given the same sign as that of the configuration of theoptical communication system 10 and the corresponding details will beomitted.

The configuration of the optical communication system according to thisembodiment is similar to that of the optical communication system 10except that a mechanical optical path switching device 280 shown inFIGS. 17A and 17B is used instead of the optical path switching device20 (refer to FIGS. 3A and 3B).

The configuration of the optical path switching device 280 is similar tothat of the optical path switching device 20 except that the reflectingmirrors 29, 30 (refer to FIGS. 3A and 3B) are removed and that lightreceiving elements 31, 32 are fixed to different positions on theplatform 22 from those in the optical path switching device 20.

As shown in FIG. 18, the light receiving element 31 is arranged in aposition on which is incident only a portion (hereinafter described as5% as an example) of light 23A outputted from an optical fibercollimator 23 in the outer part in radial direction so as to receive 5%of light outputted from the optical fiber collimator 23. Similarly, thelight receiving element 32 is arranged in a position on which isincident only a portion (hereinafter described as 5% as an example) oflight outputted from an optical fiber collimator 24 in width directionso as to receive 5% of light outputted from the optical fiber collimator24.

Next, the operation of the optical communication system according tothis embodiment will be described.

The operation of the optical communication system according to thisembodiment is almost similar to that of the optical communication system10 according to the first embodiment (refer to FIG. 1) so that thecorresponding details will be omitted.

When a controller 14 has determined that a line connected to the opticalfiber collimator 23 is not faulty, light inside the optical pathswitching device 280 travels as shown by arrows in dotted lines in FIG.17A. When the controller 14 has determined that a line connected to theoptical fiber collimator 23 is faulty, the light inside the optical pathswitching device 280 travels as shown by arrows in dotted lines in FIG.17B.

As described above, in the optical path switching device 280, the lightreceiving elements 31, 32 directly detect only a portion of lightoutputted from the optical fibers 2323 a, 24 a in the outer part inradial direction. This suppresses losses of light for monitoring andenhances the optical confinement efficiency into an optical fiber foroutput.

The optical path switching device 280 need not include the reflectingmirrors 29, 30 (refer to FIGS. 3A and 3B) unlike the optical pathswitching device 20 according to the first embodiment (refer to FIGS. 3Aand 3B). The optical path switching device 280 thus uses a smallernumber of components than the optical path switching device 20 andoffers a more compact design.

The optical path switching device 280 directly receives optical signalsoutputted from the optical fiber collimator 23, 24 respectively by wayof the light receiving elements 31, 32 thus reducing the PolarizationDependent Loss (PDL).

INDUSTRIAL APPLICABILITY

As described above, the optical path switching device of the inventionhas advantages of suppressing losses of light for monitoring andenhancing the optical confinement efficiency into an optical fiber foroutput and is useful as an optical path switching device for opticalcommunications.

FIG. 1

-   10: OPTICAL COMMUNICATION SYSTEM-   11: OPTICAL TRANSMITTER-   12: OPTICAL RECEIVER-   13: OPTICAL BRANCHING DEVICE-   14: CONTROLLER-   20: OPTICAL PATH SWITCHING DEVICE

1. An optical path switching device comprising: at least one opticalinput means including an optical fiber and a lens for inputting anoptical signal; at least one optical output means including an opticalfiber and a lens for outputting an optical signal; an optical pathswitching component for switching over the optical path between theoptical input means and the optical output means based on a change inits state; and an optical detection component for detecting a portion ofsaid light inputted from said optical inputting means in order tomonitor said light; said optical detection component controlled inaccordance with the monitoring result of said light, characterized inthat said optical detection component detects only a portion of saidlight in the outer part in radial direction.
 2. The optical pathswitching device according to claim 1, further comprising opticalbranching means for branching only a portion of said light inputted fromsaid optical input means in the outer part in radial direction,characterized in that said optical detection component detects the lightbranched by this optical branching means.
 3. The optical path switchingdevice according to claim 1, characterized in that said opticaldetection component is arranged in a position on which is directlyincident only a portion of light inputted from said optical input meansin the outer part in radial direction.